Headshaking in Horses

Your favorite horse is tacked up and ready for your daily ride. You mount up, and as soon as you begin warming up in your outdoor ring, he starts tossing his head and sneezing. The sneezing eventually stops, but every time you try to begin work, he tosses his head. You get off and apply more fly spray, thinking its just the annoying gnats and flies that are beginning to emerge, but the head tossing continues. You check your bridle and make sure the bit is in the correct place and not too tight--everything looks OK. The next day, you change bits. It must be your horse just doesn't like the taste of the new snaffle. Then your ride is the same--if not worse--than yesterday. Almost constant head tossing makes it impossible to train your horse effectively. Weeks go by, and some days are better than others, but you wonder what in the world is going on, and how am I ever going to get this horse into a dressage arena?

This is a headshaker--welcome to their world. What is headshaking and what compels horses to toss their heads over and over? And what can be done to stop it? For answers to these questions and more, read on.

What Is Headshaking?

Horses shaking their heads might not seem like a big problem. Horses shake their heads all the time, usually while outside in the paddock or in their stalls in an attempt to avoid insects that pester their face and muzzle. So what's the big deal? Headshaking, however, is different. It takes on a whole new meaning when this behavior is performed frequently, if not constantly, while the horse is being ridden, and nothing about this behavior is normal. Headshaking is the act of the horse flipping its nose into the air, sometimes even shaking its head from side to side. This type of headshaking, the pathologic manifestation, also often involves rubbing the muzzle and sneezing. Not only is this behavior irritating and uncontrollable, but can seriously hamper the ability of the horse to perform in many disciplines. Some horses even become dangerous as their headshaking takes on an obsessive and violent form. These horses might appear as if a bee has flown up their nose.

What Causes Headshaking?

Although this disorder has been reported to occur in horses for decades, one exact etiology has never been elucidated. If you own a headshaker, don't despair, we know there are several factors that can cause horses to shake their heads, and there is a list of differential diagnoses that should be investigated before you give up on your headshaker.

Until recently, many people gave up on their headshaking horses. There did not seem to be anything that stopped the behavior, making it impossible to enjoy riding that horse. For many years, people surmised that headshaking was purely a rider or training problem, not a medical disorder. Some people believed that the headshaking was caused by ill-fitting tack (the bit or bridle) or a rider with heavy or bad hands jabbing the horse in the mouth. Still others believed it was purely a training problem of a learned behavior--that the horse learned that if it shook its head, the rider would soon dismount.

As veterinarians began realizing that this was a medical problem, one early theory was allergies or irritation by pollen or dirt inhaled in the nose, tickling the horse's sensitive nostrils and causing the horse to toss his head and/or sneeze. Treatments included placing panty hose or some type of filter over the horse's nose in an attempt to filter out allergens and/or small dust particles. This actually helped some horses. Although this was a fine treatment at home, pantyhose on your horse's head in the show ring usually doesn't result in ribbons.

Another theory tested was that tingling or some other odd sensation within the inside of the nostrils resulted in the headshaking. The tingling was thought to be due to inhaled particles, allergies, or some other unknown factor resulting in a sensation that caused the horse to shake his head. The infraorbital nerve was blocked with a local anesthetic (just like nerve blocks performed on a horse's leg to diagnose lameness). The infraorbital nerve is present beginning at the infraorbital foramen (about half-way down the nose), and when this area is blocked, it desensitizes the inside of both nostrils. The horses then were exercised outside--if the headshaking was greatly decreased or stopped, then they were considered a candidate for an infraorbital neurectomy. This surgery transected the infraorbital nerve, which resulted in a lack of sensation on the inside of both nostrils, and for some horses it gave relief to the headshaking. Other horses were not as fortunate, and the surgery was not successful. This procedure is not performed very often these days since a newer medical treatment has proven more successful.

What To Do

If you own or care for a headshaker and the behavior persists despite fly control and properly fitted tack, you should contact your veterinarian. A thorough physical examination should be performed and the horse ridden so your veterinarian can observe the headshaking behavior. Questions you should be prepared to answer include: When does the behavior occur most frequently--while the horse is inside or outside? Is the headshaking better or worse on an overcast day or in an indoor riding ring? When did the behavior begin? If the headshaking is chronic, did the behavior resolve over the wintertime? In other words, does this seem to be a seasonal problem?

Based on the answers to these and other questions, your veterinarian will formulate a plan to determine the cause of the headshaking. Causes for headshaking include ear mites, ocular problems, fungal infection of the guttural pouch, middle ear infections, nasal and/or dental problems, and a disorder called photic headshaking.

Your veterinarian will go through the list of potential causes and determine which is most likely causing your horse to shake his head. Several procedures, such as radiographs of the head, endoscopy of the upper airway, an ophthalmic examination, or an oral examination, might be needed in addition to a good physical examination. Unfortunately, even if one of the above-mentioned problems is found, treatment for the disorder might not stop the headshaking.

Many veterinarians believe that horses with seasonal headshaking, or horses in which the headshaking becomes worse in direct sunlight, shake their heads for the same reason some people sneeze when in direct sunlight (called the photic sneeze). These horses are called photic headshakers, which means that direct sunlight causes the headshaking.

What Is Photic Headshaking?

John Madigan, DVM, MS, Dipl. ACVIM, from the University of California, Davis, has done a great deal of research on photic headshaking in horses and has reported on these horses in several articles. Madigan and fellow researchers believe that horses shake their heads from the bright light due to an abnormal stimulation of some of the branches of the trigeminal nerve, which provides sensation to the face and muzzle. The light stimulation of the eye causes an abnormal stimulation of some of the nerves of the face and muzzle and results in actual tingling or even pain sensation in some horses, which causes them to violently shake and rub their heads.

The reason that these horses have facial pain resulting from direct sunlight is still unknown. One theory is that a previous facial injury has resulted in abnormal nerve transmission. For these photic headshaking horses, avoiding bright light, keeping them in dark stalls, even riding at night eliminates this behavior completely. Other horses are helped by using eye protection (sunglasses) during bright light.

What Can You Do?

So, you have a headshaker, and he does get better in indirect or dim light; riding him at night in an indoor ring does eliminate the behavior, but you can't ride in the dark forever. For these photic headshakers, there is a treatment that might help. At the 1997 convention of the American Association of Equine Practitioners, Madigan reported on the results of a pharmaceutical treatment for headshakers.

A drug called Cyproheptadine, which is a histamine and serotonin blocking agent, was administered to a group of 25 headshakers. This drug resulted in moderate to great improvement in 76% of the horses. Al-though it is unknown exactly how the drug worked to decrease the headshaking, it was thought that the drug mediated sensation in the affected facial and muzzle nerve branches, therefore decreasing the headshaking. If the name of this drug seems familiar, Cyproheptadine also is used to treat horses and ponies with Cushing's disease.

If this drug does work for a headshaker, however, the duration of treatment is variable. Some horses will need to be administered the drug indefinitely, while others will need only seasonal treatment. Furthermore, some horses will need to be protected from the sunlight in addition to being medicated. In any case, working closely with your veterinarian will help you to find the best treatment regimen to help your horse.

Headshaking in horses can be a very frustrating problem for owner and veterinarian. But with the Cyproheptadine treatment, more and more horses and their riders are able to overcome this often career ending problem.

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